Virtually no medicinal herb has been established as safe in pregnancy or breast-feeding, and even herbs that might seem safe because of their wide use in cooking could cause problems when they are taken in the form of highly concentrated extracts. For example, based on food use it is unlikely that cookedgarlic presents much risk; however, garlic supplements contain certain rather potent and potentially toxic ingredients present only in raw garlic. Few people eat large quantities of raw garlic on a regular basis, and therefore there is no long history of use to reassure us.

Modern research has raised concerns about many other herbs as well. For example, the herb chasteberry has shown a theoretical potential for inhibiting milk supply. In addition, herbs with estrogen-like properties make scientists worry about possible effects on the fetus; these include soy , isoflavones , red clover , flaxseed , lignans , and hops .

There are also theoretical concerns that high intake of green tea could increase risk of birth defects by interfering with folate levels . 12

Further health concerns exist with traditional Chinese herbal combinations , and Ayurvedic herbal combinations . These products have been found on occasion to contain toxic heavy metals, poisonous herbs, or unlabelled prescription drugs. 4,11 For example, in one case report, a brain-damaged child born to a mother using an Ayurvedic formula was found to have the highest bloods levels of lead ever recorded in a living newborn. 11 Analysis of the formula revealed a very high lead content, along with toxic levels of mercury. In general, it is probably accurate to say that noherb can be regarded as definitely benign. 2

Supplements that are essential nutrients, such as vitamins, generally have a known maximum safe intake level during pregnancy and nursing, and these are discussed in the relevant articles in this database. However, other supplements that are not essential nutrients are in much the same position as herbs, and could conceivably cause harm. For example, the supplement CLA (conjugated linoleic acid) appears to reduce the fat content of breast milk, with potentially harmful effects on the nursing infant, 3chitosan may cause impaired nutrient absorption, and at times may contain arsenic. (Contamination with toxic substances is also a real possibility with one nutrient supplement: certain calcium supplements have been found to contain high levels of lead.)

Nonetheless, many herbs and supplements have a high enough safety factor that researchers have felt comfortable giving them to pregnant women. For more information on a particular herb or supplement, see its entry in the Herbs & Supplements database of this database.